Well if you read that in any rules it would not have neen the IMPBA's FE rules as there are not any official "SPEC" or "Limited" classes in IMPBA.

However, I would think that would pertain to RTR boats since this is presumably an RC boating organization where you read these rules. Besides this the motors used in "Limited" are the 36-56 size and I would say most if not all these truck motors are much bigger. If these were allowed it would just be another P class and the moniker "Limited" would not mean anything.